Making deting oils



Patented Jan. 26, 1943 MAKING DRYING OILS Remmet Priester, Deventer, Netherlands; vested in the Alien Property Custodian No Drawing. Application October 24, 1940, Serial In the Netherlands January 6,

6 Claims. (Cl. 260-398) The presentinvention relates to the manufacture of drying oils from glyceride oils having one or more hydroxyl groups in the fatty acid radiheating at a temperature of say 300 C. into an unsaturated acid with two double bonds in a conjugated neighbouring position and thereafter esterifying the acid thus obtained with a suitable alcohol. 1

For obviousreasons, a process which causes the splitting off of water from the -hydroxyl groups of the hydroxy fatty acid radicals present in the castor or like oil, without causing liberation of any considerable amount of free acid from the glyceride oil, is advantageous. Such a reaction has heretofore been suggested, using sulphuric acid or certain other substances as the catalyst. Among the very satisfactory catalysts originally described in my earlier cases (including Ser. No. 181,467 filed Dec. 23, 1937, of which the present case is in major part 'a continuation and which has now matured into Patent 2,226,830,) may be mentioned pyrosulphate such as K2820: potassium pyrosulpl'iate.

Alkali metal pyrosulphate, such as the sodium and potassium, are very useful, and possess important advantages over many of the catalysts proposed in the prior art, particularly in that the said substances are solids that do not melt or liquefy during ordinary running of the process, they can accordingly be easily and readily and completely removed from the oil after the heating operation, they can be employed without causing undesirable darkening of the oil under treatment, they are cheap and can be produced easily and cheaply and from materials that are readily available everywhere (e. g. alkali metal bisulphate including alter-cake or alkali metal sulphate or many other commonly found alkali metal salts and sulphuric acid), and the drying oils produced may have a desirably low acid number.

Formore compleuely describing the process, I givle the following specific example, from Ser. No. 18 .487: a j

Example First part.-Castor oil is stirred with 1% by weight of finely divided potassium pyrosulphate, and heated under vacuum whilst passing carbon dioxide through the liquid at a temperature from 180-240 C. for 4 hours. The temperature is slowly raised during the heating process until the distillation of water has ceased.

Second port-The mixture may then be further heated for 3 hours at a temperature of 280 C. under the same working conditions in order to form a stand 011. After elimination of the catalyst in the usual way (e. g. by filtration or straining) a high grade drying oil product is obtained with valuable technical properties.

The product of the first part" of the process (if filtered from the pyrosulphate) is a drying oil, light in color, of strong drying properties and with an acid number very little above that of the castor oil employed as starting material.

Instead of castor 011, other oils which are esters of hydroxy fatty acids can be treated by this process to produce drying oils, e. g. ,thetriglyceride of dihydroxystearic .acid. a

It will be understood that a small percentage of the pyrosulphate is sufiicient, e. g. from 0.1% to 5% may be employed, but preferably 0.2% to 1.5% is most satisfactory. Instead of the potassium salt, the sodium salt, or mixture of the sodium and potassium salts are also suitable;

The temperatures given in the example are suitable and satisfactory, but various temperatures in the first part of the process substantially over C. and up to 260 C. may be used. In the second part of the process, temperatures over 260 0., up to 300 (2., may be used. It is hardly necessary to state that the higher temperatures, especially it continued for a long time,

may cause a higher acidity of the oil.

The time element given in the example is satisfactory. But, with somewhat higher temperatures, correspondingly shorter time periods can be used.

The carbon dioxide can be replaced by other ity, and usable-for all the common uses of drying oils.

As set forth in my copending case 181,468 filed December 23, 1937 (now Patent 2,226,831), there may be a substantial rise in acid number in the oil, during the second part of the process, and this can be prevented by adding glycerol to the oil, before or during or after the first part of the process, and before the second part of the'process. The amount of such glycerol may be about 1% or from 0.5 to 3%, more or less. Other not easily volatile active alcohols can be similarly used, e. g. sorbitol, cetyl alcohol, glycol, pentaerythritol, r alkylene oxides such as ethylene oxide can be introduced into the oil, e. g. with the current of inert gas, during the second part of the process.

The drying oil produced by the present process has excellent drying properties, similar to those of Chinese tung oil, and shows a very fine light yellow color. With driers added, a film of the oil dries rapidly, to a strong film. A stand oil can be produced from these drying oils, e. g. as in the second part of the above example. The temperature for the formation may be 260-300 C., preferably 270 to 280 C.

I claim:

1. A process of making a drying oil which comprises heating a glyceride oil which is an ester of'a hydroxy fatty acid, in the presence of a small amount of a pyrosulphateas a dehydrating catalyst, to a temperature substantially above 150 C., for a sufficient time to cause splitting off of water from the hydroxyl groups of the hydroxy fatty acid radical, and continuing the heating until substantial drying properties are developed in the oil, the pyrosulphate being one that is a solid and which remains solid throughout the process.

2. A process of making a drying oil which comprises heating castor oil with not more than a few percent of an alkali metal pyrosulphate, to over C., until an oil having drying properties is produced.

3. A process of making a drying oil which comprises heating castor oil with not more than a few percent of an alkali metal pyrosulphate, to substantially over 150 C., while passing a current of an inert gas through said oil, until an oil having drying properties is produced.

4. A process of making a drying oil which comprises heating castor oil with not more than a few percent of an alkali metal pyrosulphate, to substantiallyover 150 C., while the oil is under a pressure substantially below atmospheric, until an oil having drying properties is produced. 7

5. A process of making a drying oil which comprises heating castor oil mixed with not more than a few percent of pyrosulphate of an alkali metal, to about to 240 C., for about 4 hours, while said oil is under vacuum and while passing a current of an inert gas through said oil.

6. A process of making a drying oil which comprises heating castor oil mixed with not more than a few percent of a pyrosulphate of an alkali metal, to about 180 to 240 C., for about 4 hours, while said oil is under vacuum and while passing a current of an inert gas through said oil, and thereafter heating the said material to about 270 to 300 C., until thickening to stand oil consistency is effected.

REMMET PRIESTER. 

